 Field-squared quadrature

Hermitian combinations of pair creation and annihilation operators. With $K_3=(N+1/2)/2$, their commutators are $[K_1,K_2]=-4i{K}_3$, $[K_2,K_3]=i{K}_1$ and $[K_3,K_1]=i{K}_2$. A coherent state has both variances $⟨N⟩+1/2$, saturating the corresponding uncertainty product.